U.S. Pat. Nos. 5,241,940 (Gates, Jr.) and 5,613,479 (Gates et al.), which are hereby incorporated by reference, disclose EGR systems of the type in which a module that can be tested and calibrated according to principles of the present invention is useful. Such a module possesses a construction that provides important economic and functional advantages relating to fabrication, assembly, testing, installation, and use, and certain principles of the present invention relate to the testing and calibration of such a module.